The IPCC says there is mounting evidence - but the science may need "revision"

By environment correspondent Alex Kirby

A draft report by United Nations advisers says deciding how to tackle climate change is shrouded in uncertainty.

It urges "a prudent risk management strategy" and "careful consideration of the consequences, both environmental and economic".

The report, on mitigating climate change, has been passed to BBC News Online. It is to be published in March.

It says policymakers should be ready for "possible revision of the scientific insights into the risks of climate change".

The report is being finalised by the UN's Intergovernmental Panel on Climate Change (IPCC), and is certain to be changed before publication.

Hesitant approach

Last month, an IPCC report on the science of climate change said the world was warming faster than previously predicted, and found increasingly strong evidence for human activities as a cause.

The thirst for oil will not slacken

Another report this month, on the impacts of climate change, was the IPCC's strongest and most detailed warning so far of what global warming might mean.

But the draft report on mitigation, by contrast, emphasises the uncertainties involved and the need not to decide policy without more information.

It says: "Climate change decision-making is essentially a sequential process under uncertainty . . . it should consider appropriate hedging" until there is agreement on the level at which greenhouse gas emissions should be stabilised.

Among the report's detailed findings are:

nuclear power can help significantly to bring greenhouse emissions down over the next 20 years;

the technology already exists to stabilise the atmospheric concentration of carbon dioxide (C02) at between 450 and 550 parts per million: the present concentration is about 370 ppm, a third more than pre-industrial levels;

it would cost "substantially" more to stabilise CO2 at 450 ppm than at 750 ppm;

the global demand for oil will probably increase, whether or not governments reduce emissions as they agreed under the Kyoto Protocol.

The marked contrast between this report and those on the science and impacts of climate change has dismayed some experts.

'Climate Rottweiler'

The Chartered Insurance Institute (CII), the leading professional body for insurance and financial services, has published a report on climate change.

It concludes: "The key message is that climate change is now a proven fact."

Nuclear power can help

A CII briefing says governments should adopt a policy of contraction and convergence as "the most realistic way" to control greenhouse gases.

This argues, in essence, that everyone in the world has an equal right to emit greenhouse gases, but that total emissions should be kept below the level where they intensify global warming.

The leader of the group that produced the CII report is Dr Andrew Dlugolecki, visiting research fellow at the Climate Research Unit, University of East Anglia, UK. He says hesitancy in the face of the IPCC's mounting evidence will unleash "a climate Rottweiler".

Dr Dlugolecki told BBC News Online: "I'm frustrated with the lack of progress in the IPCC process. There's no drive, no sense of urgency that we have to get a move on. "The Kyoto emission cuts of 5.2% are only playing for time, and we haven't even achieved them yet.

Boomerang effect

"I'd hope that this mitigation report would call for urgent and serious action going beyond Kyoto, instead of this milk-and-water stuff.

"We know climate change is happening, but we won't know for about 20 years how serious it's going to be, and that's frightening.

"It means we just have to start taking decisions before we know the full position.

"Climate change is like a boomerang. You chuck it, nothing happens for a considerable time - and then it comes back and hits you."